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-rw-r--r--arch/x86/kernel/cpu/resctrl/rdtgroup.c65
-rw-r--r--fs/kernfs/dir.c96
-rw-r--r--fs/kernfs/kernfs-internal.h32
-rw-r--r--fs/kernfs/mount.c10
-rw-r--r--fs/kernfs/symlink.c23
-rw-r--r--fs/sysfs/file.c24
-rw-r--r--include/linux/kernfs.h10
-rw-r--r--kernel/cgroup/cgroup-v1.c2
-rw-r--r--kernel/cgroup/cgroup.c24
-rw-r--r--tools/testing/selftests/bpf/progs/profiler.inc.h2
10 files changed, 195 insertions, 93 deletions
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 6419e04d8a7b..55dcdeea1a1b 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -956,10 +956,20 @@ static int rdt_last_cmd_status_show(struct kernfs_open_file *of,
return 0;
}
+static void *rdt_kn_parent_priv(struct kernfs_node *kn)
+{
+ /*
+ * The parent pointer is only valid within RCU section since it can be
+ * replaced.
+ */
+ guard(rcu)();
+ return rcu_dereference(kn->__parent)->priv;
+}
+
static int rdt_num_closids_show(struct kernfs_open_file *of,
struct seq_file *seq, void *v)
{
- struct resctrl_schema *s = of->kn->parent->priv;
+ struct resctrl_schema *s = rdt_kn_parent_priv(of->kn);
seq_printf(seq, "%u\n", s->num_closid);
return 0;
@@ -968,7 +978,7 @@ static int rdt_num_closids_show(struct kernfs_open_file *of,
static int rdt_default_ctrl_show(struct kernfs_open_file *of,
struct seq_file *seq, void *v)
{
- struct resctrl_schema *s = of->kn->parent->priv;
+ struct resctrl_schema *s = rdt_kn_parent_priv(of->kn);
struct rdt_resource *r = s->res;
seq_printf(seq, "%x\n", r->default_ctrl);
@@ -978,7 +988,7 @@ static int rdt_default_ctrl_show(struct kernfs_open_file *of,
static int rdt_min_cbm_bits_show(struct kernfs_open_file *of,
struct seq_file *seq, void *v)
{
- struct resctrl_schema *s = of->kn->parent->priv;
+ struct resctrl_schema *s = rdt_kn_parent_priv(of->kn);
struct rdt_resource *r = s->res;
seq_printf(seq, "%u\n", r->cache.min_cbm_bits);
@@ -988,7 +998,7 @@ static int rdt_min_cbm_bits_show(struct kernfs_open_file *of,
static int rdt_shareable_bits_show(struct kernfs_open_file *of,
struct seq_file *seq, void *v)
{
- struct resctrl_schema *s = of->kn->parent->priv;
+ struct resctrl_schema *s = rdt_kn_parent_priv(of->kn);
struct rdt_resource *r = s->res;
seq_printf(seq, "%x\n", r->cache.shareable_bits);
@@ -1012,7 +1022,7 @@ static int rdt_shareable_bits_show(struct kernfs_open_file *of,
static int rdt_bit_usage_show(struct kernfs_open_file *of,
struct seq_file *seq, void *v)
{
- struct resctrl_schema *s = of->kn->parent->priv;
+ struct resctrl_schema *s = rdt_kn_parent_priv(of->kn);
/*
* Use unsigned long even though only 32 bits are used to ensure
* test_bit() is used safely.
@@ -1094,7 +1104,7 @@ static int rdt_bit_usage_show(struct kernfs_open_file *of,
static int rdt_min_bw_show(struct kernfs_open_file *of,
struct seq_file *seq, void *v)
{
- struct resctrl_schema *s = of->kn->parent->priv;
+ struct resctrl_schema *s = rdt_kn_parent_priv(of->kn);
struct rdt_resource *r = s->res;
seq_printf(seq, "%u\n", r->membw.min_bw);
@@ -1104,7 +1114,7 @@ static int rdt_min_bw_show(struct kernfs_open_file *of,
static int rdt_num_rmids_show(struct kernfs_open_file *of,
struct seq_file *seq, void *v)
{
- struct rdt_resource *r = of->kn->parent->priv;
+ struct rdt_resource *r = rdt_kn_parent_priv(of->kn);
seq_printf(seq, "%d\n", r->num_rmid);
@@ -1114,7 +1124,7 @@ static int rdt_num_rmids_show(struct kernfs_open_file *of,
static int rdt_mon_features_show(struct kernfs_open_file *of,
struct seq_file *seq, void *v)
{
- struct rdt_resource *r = of->kn->parent->priv;
+ struct rdt_resource *r = rdt_kn_parent_priv(of->kn);
struct mon_evt *mevt;
list_for_each_entry(mevt, &r->evt_list, list) {
@@ -1129,7 +1139,7 @@ static int rdt_mon_features_show(struct kernfs_open_file *of,
static int rdt_bw_gran_show(struct kernfs_open_file *of,
struct seq_file *seq, void *v)
{
- struct resctrl_schema *s = of->kn->parent->priv;
+ struct resctrl_schema *s = rdt_kn_parent_priv(of->kn);
struct rdt_resource *r = s->res;
seq_printf(seq, "%u\n", r->membw.bw_gran);
@@ -1139,7 +1149,7 @@ static int rdt_bw_gran_show(struct kernfs_open_file *of,
static int rdt_delay_linear_show(struct kernfs_open_file *of,
struct seq_file *seq, void *v)
{
- struct resctrl_schema *s = of->kn->parent->priv;
+ struct resctrl_schema *s = rdt_kn_parent_priv(of->kn);
struct rdt_resource *r = s->res;
seq_printf(seq, "%u\n", r->membw.delay_linear);
@@ -1157,7 +1167,7 @@ static int max_threshold_occ_show(struct kernfs_open_file *of,
static int rdt_thread_throttle_mode_show(struct kernfs_open_file *of,
struct seq_file *seq, void *v)
{
- struct resctrl_schema *s = of->kn->parent->priv;
+ struct resctrl_schema *s = rdt_kn_parent_priv(of->kn);
struct rdt_resource *r = s->res;
if (r->membw.throttle_mode == THREAD_THROTTLE_PER_THREAD)
@@ -1222,7 +1232,7 @@ static enum resctrl_conf_type resctrl_peer_type(enum resctrl_conf_type my_type)
static int rdt_has_sparse_bitmasks_show(struct kernfs_open_file *of,
struct seq_file *seq, void *v)
{
- struct resctrl_schema *s = of->kn->parent->priv;
+ struct resctrl_schema *s = rdt_kn_parent_priv(of->kn);
struct rdt_resource *r = s->res;
seq_printf(seq, "%u\n", r->cache.arch_has_sparse_bitmasks);
@@ -1634,7 +1644,7 @@ static int mbm_config_show(struct seq_file *s, struct rdt_resource *r, u32 evtid
static int mbm_total_bytes_config_show(struct kernfs_open_file *of,
struct seq_file *seq, void *v)
{
- struct rdt_resource *r = of->kn->parent->priv;
+ struct rdt_resource *r = rdt_kn_parent_priv(of->kn);
mbm_config_show(seq, r, QOS_L3_MBM_TOTAL_EVENT_ID);
@@ -1644,7 +1654,7 @@ static int mbm_total_bytes_config_show(struct kernfs_open_file *of,
static int mbm_local_bytes_config_show(struct kernfs_open_file *of,
struct seq_file *seq, void *v)
{
- struct rdt_resource *r = of->kn->parent->priv;
+ struct rdt_resource *r = rdt_kn_parent_priv(of->kn);
mbm_config_show(seq, r, QOS_L3_MBM_LOCAL_EVENT_ID);
@@ -1750,7 +1760,7 @@ static ssize_t mbm_total_bytes_config_write(struct kernfs_open_file *of,
char *buf, size_t nbytes,
loff_t off)
{
- struct rdt_resource *r = of->kn->parent->priv;
+ struct rdt_resource *r = rdt_kn_parent_priv(of->kn);
int ret;
/* Valid input requires a trailing newline */
@@ -1776,7 +1786,7 @@ static ssize_t mbm_local_bytes_config_write(struct kernfs_open_file *of,
char *buf, size_t nbytes,
loff_t off)
{
- struct rdt_resource *r = of->kn->parent->priv;
+ struct rdt_resource *r = rdt_kn_parent_priv(of->kn);
int ret;
/* Valid input requires a trailing newline */
@@ -2440,12 +2450,13 @@ static struct rdtgroup *kernfs_to_rdtgroup(struct kernfs_node *kn)
* resource. "info" and its subdirectories don't
* have rdtgroup structures, so return NULL here.
*/
- if (kn == kn_info || kn->parent == kn_info)
+ if (kn == kn_info ||
+ rcu_access_pointer(kn->__parent) == kn_info)
return NULL;
else
return kn->priv;
} else {
- return kn->parent->priv;
+ return rdt_kn_parent_priv(kn);
}
}
@@ -3771,9 +3782,18 @@ static int rdtgroup_rmdir_ctrl(struct rdtgroup *rdtgrp, cpumask_var_t tmpmask)
return 0;
}
+static struct kernfs_node *rdt_kn_parent(struct kernfs_node *kn)
+{
+ /*
+ * Valid within the RCU section it was obtained or while rdtgroup_mutex
+ * is held.
+ */
+ return rcu_dereference_check(kn->__parent, lockdep_is_held(&rdtgroup_mutex));
+}
+
static int rdtgroup_rmdir(struct kernfs_node *kn)
{
- struct kernfs_node *parent_kn = kn->parent;
+ struct kernfs_node *parent_kn;
struct rdtgroup *rdtgrp;
cpumask_var_t tmpmask;
int ret = 0;
@@ -3786,6 +3806,7 @@ static int rdtgroup_rmdir(struct kernfs_node *kn)
ret = -EPERM;
goto out;
}
+ parent_kn = rdt_kn_parent(kn);
/*
* If the rdtgroup is a ctrl_mon group and parent directory
@@ -3854,6 +3875,7 @@ static void mongrp_reparent(struct rdtgroup *rdtgrp,
static int rdtgroup_rename(struct kernfs_node *kn,
struct kernfs_node *new_parent, const char *new_name)
{
+ struct kernfs_node *kn_parent;
struct rdtgroup *new_prdtgrp;
struct rdtgroup *rdtgrp;
cpumask_var_t tmpmask;
@@ -3888,8 +3910,9 @@ static int rdtgroup_rename(struct kernfs_node *kn,
goto out;
}
- if (rdtgrp->type != RDTMON_GROUP || !kn->parent ||
- !is_mon_groups(kn->parent, kn->name)) {
+ kn_parent = rdt_kn_parent(kn);
+ if (rdtgrp->type != RDTMON_GROUP || !kn_parent ||
+ !is_mon_groups(kn_parent, kn->name)) {
rdt_last_cmd_puts("Source must be a MON group\n");
ret = -EPERM;
goto out;
diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index 43fbada67838..1d370c497e8a 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -17,7 +17,7 @@
#include "kernfs-internal.h"
-static DEFINE_RWLOCK(kernfs_rename_lock); /* kn->parent and ->name */
+DEFINE_RWLOCK(kernfs_rename_lock); /* kn->parent and ->name */
/*
* Don't use rename_lock to piggy back on pr_cont_buf. We don't want to
* call pr_cont() while holding rename_lock. Because sometimes pr_cont()
@@ -56,7 +56,7 @@ static int kernfs_name_locked(struct kernfs_node *kn, char *buf, size_t buflen)
if (!kn)
return strscpy(buf, "(null)", buflen);
- return strscpy(buf, kn->parent ? kn->name : "/", buflen);
+ return strscpy(buf, rcu_access_pointer(kn->__parent) ? kn->name : "/", buflen);
}
/* kernfs_node_depth - compute depth from @from to @to */
@@ -64,9 +64,9 @@ static size_t kernfs_depth(struct kernfs_node *from, struct kernfs_node *to)
{
size_t depth = 0;
- while (to->parent && to != from) {
+ while (rcu_dereference(to->__parent) && to != from) {
depth++;
- to = to->parent;
+ to = rcu_dereference(to->__parent);
}
return depth;
}
@@ -84,18 +84,18 @@ static struct kernfs_node *kernfs_common_ancestor(struct kernfs_node *a,
db = kernfs_depth(rb->kn, b);
while (da > db) {
- a = a->parent;
+ a = rcu_dereference(a->__parent);
da--;
}
while (db > da) {
- b = b->parent;
+ b = rcu_dereference(b->__parent);
db--;
}
/* worst case b and a will be the same at root */
while (b != a) {
- b = b->parent;
- a = a->parent;
+ b = rcu_dereference(b->__parent);
+ a = rcu_dereference(a->__parent);
}
return a;
@@ -168,8 +168,9 @@ static int kernfs_path_from_node_locked(struct kernfs_node *kn_to,
/* Calculate how many bytes we need for the rest */
for (i = depth_to - 1; i >= 0; i--) {
+
for (kn = kn_to, j = 0; j < i; j++)
- kn = kn->parent;
+ kn = rcu_dereference(kn->__parent);
len += scnprintf(buf + len, buflen - len, "/%s", kn->name);
}
@@ -226,6 +227,7 @@ int kernfs_path_from_node(struct kernfs_node *to, struct kernfs_node *from,
unsigned long flags;
int ret;
+ guard(rcu)();
read_lock_irqsave(&kernfs_rename_lock, flags);
ret = kernfs_path_from_node_locked(to, from, buf, buflen);
read_unlock_irqrestore(&kernfs_rename_lock, flags);
@@ -295,7 +297,7 @@ struct kernfs_node *kernfs_get_parent(struct kernfs_node *kn)
unsigned long flags;
read_lock_irqsave(&kernfs_rename_lock, flags);
- parent = kn->parent;
+ parent = kernfs_parent(kn);
kernfs_get(parent);
read_unlock_irqrestore(&kernfs_rename_lock, flags);
@@ -360,8 +362,12 @@ static int kernfs_sd_compare(const struct kernfs_node *left,
*/
static int kernfs_link_sibling(struct kernfs_node *kn)
{
- struct rb_node **node = &kn->parent->dir.children.rb_node;
struct rb_node *parent = NULL;
+ struct kernfs_node *kn_parent;
+ struct rb_node **node;
+
+ kn_parent = kernfs_parent(kn);
+ node = &kn_parent->dir.children.rb_node;
while (*node) {
struct kernfs_node *pos;
@@ -380,13 +386,13 @@ static int kernfs_link_sibling(struct kernfs_node *kn)
/* add new node and rebalance the tree */
rb_link_node(&kn->rb, parent, node);
- rb_insert_color(&kn->rb, &kn->parent->dir.children);
+ rb_insert_color(&kn->rb, &kn_parent->dir.children);
/* successfully added, account subdir number */
down_write(&kernfs_root(kn)->kernfs_iattr_rwsem);
if (kernfs_type(kn) == KERNFS_DIR)
- kn->parent->dir.subdirs++;
- kernfs_inc_rev(kn->parent);
+ kn_parent->dir.subdirs++;
+ kernfs_inc_rev(kn_parent);
up_write(&kernfs_root(kn)->kernfs_iattr_rwsem);
return 0;
@@ -407,16 +413,19 @@ static int kernfs_link_sibling(struct kernfs_node *kn)
*/
static bool kernfs_unlink_sibling(struct kernfs_node *kn)
{
+ struct kernfs_node *kn_parent;
+
if (RB_EMPTY_NODE(&kn->rb))
return false;
+ kn_parent = kernfs_parent(kn);
down_write(&kernfs_root(kn)->kernfs_iattr_rwsem);
if (kernfs_type(kn) == KERNFS_DIR)
- kn->parent->dir.subdirs--;
- kernfs_inc_rev(kn->parent);
+ kn_parent->dir.subdirs--;
+ kernfs_inc_rev(kn_parent);
up_write(&kernfs_root(kn)->kernfs_iattr_rwsem);
- rb_erase(&kn->rb, &kn->parent->dir.children);
+ rb_erase(&kn->rb, &kn_parent->dir.children);
RB_CLEAR_NODE(&kn->rb);
return true;
}
@@ -562,7 +571,7 @@ void kernfs_put(struct kernfs_node *kn)
* Moving/renaming is always done while holding reference.
* kn->parent won't change beneath us.
*/
- parent = kn->parent;
+ parent = kernfs_parent(kn);
WARN_ONCE(atomic_read(&kn->active) != KN_DEACTIVATED_BIAS,
"kernfs_put: %s/%s: released with incorrect active_ref %d\n",
@@ -701,7 +710,7 @@ struct kernfs_node *kernfs_new_node(struct kernfs_node *parent,
name, mode, uid, gid, flags);
if (kn) {
kernfs_get(parent);
- kn->parent = parent;
+ rcu_assign_pointer(kn->__parent, parent);
}
return kn;
}
@@ -769,13 +778,14 @@ err_unlock:
*/
int kernfs_add_one(struct kernfs_node *kn)
{
- struct kernfs_node *parent = kn->parent;
- struct kernfs_root *root = kernfs_root(parent);
+ struct kernfs_root *root = kernfs_root(kn);
struct kernfs_iattrs *ps_iattr;
+ struct kernfs_node *parent;
bool has_ns;
int ret;
down_write(&root->kernfs_rwsem);
+ parent = kernfs_parent(kn);
ret = -EINVAL;
has_ns = kernfs_ns_enabled(parent);
@@ -949,6 +959,11 @@ struct kernfs_node *kernfs_walk_and_get_ns(struct kernfs_node *parent,
return kn;
}
+unsigned int kernfs_root_flags(struct kernfs_node *kn)
+{
+ return kernfs_root(kn)->flags;
+}
+
/**
* kernfs_create_root - create a new kernfs hierarchy
* @scops: optional syscall operations for the hierarchy
@@ -1112,7 +1127,7 @@ struct kernfs_node *kernfs_create_empty_dir(struct kernfs_node *parent,
static int kernfs_dop_revalidate(struct inode *dir, const struct qstr *name,
struct dentry *dentry, unsigned int flags)
{
- struct kernfs_node *kn;
+ struct kernfs_node *kn, *parent;
struct kernfs_root *root;
if (flags & LOOKUP_RCU)
@@ -1163,8 +1178,9 @@ static int kernfs_dop_revalidate(struct inode *dir, const struct qstr *name,
if (!kernfs_active(kn))
goto out_bad;
+ parent = kernfs_parent(kn);
/* The kernfs node has been moved? */
- if (kernfs_dentry_node(dentry->d_parent) != kn->parent)
+ if (kernfs_dentry_node(dentry->d_parent) != parent)
goto out_bad;
/* The kernfs node has been renamed */
@@ -1172,7 +1188,7 @@ static int kernfs_dop_revalidate(struct inode *dir, const struct qstr *name,
goto out_bad;
/* The kernfs node has been moved to a different namespace */
- if (kn->parent && kernfs_ns_enabled(kn->parent) &&
+ if (parent && kernfs_ns_enabled(parent) &&
kernfs_info(dentry->d_sb)->ns != kn->ns)
goto out_bad;
@@ -1365,7 +1381,7 @@ static struct kernfs_node *kernfs_next_descendant_post(struct kernfs_node *pos,
return kernfs_leftmost_descendant(rb_to_kn(rbn));
/* no sibling left, visit parent */
- return pos->parent;
+ return kernfs_parent(pos);
}
static void kernfs_activate_one(struct kernfs_node *kn)
@@ -1377,7 +1393,7 @@ static void kernfs_activate_one(struct kernfs_node *kn)
if (kernfs_active(kn) || (kn->flags & (KERNFS_HIDDEN | KERNFS_REMOVING)))
return;
- WARN_ON_ONCE(kn->parent && RB_EMPTY_NODE(&kn->rb));
+ WARN_ON_ONCE(rcu_access_pointer(kn->__parent) && RB_EMPTY_NODE(&kn->rb));
WARN_ON_ONCE(atomic_read(&kn->active) != KN_DEACTIVATED_BIAS);
atomic_sub(KN_DEACTIVATED_BIAS, &kn->active);
@@ -1447,7 +1463,7 @@ void kernfs_show(struct kernfs_node *kn, bool show)
static void __kernfs_remove(struct kernfs_node *kn)
{
- struct kernfs_node *pos;
+ struct kernfs_node *pos, *parent;
/* Short-circuit if non-root @kn has already finished removal. */
if (!kn)
@@ -1459,7 +1475,7 @@ static void __kernfs_remove(struct kernfs_node *kn)
* This is for kernfs_remove_self() which plays with active ref
* after removal.
*/
- if (kn->parent && RB_EMPTY_NODE(&kn->rb))
+ if (kernfs_parent(kn) && RB_EMPTY_NODE(&kn->rb))
return;
pr_debug("kernfs %s: removing\n", kn->name);
@@ -1485,14 +1501,14 @@ static void __kernfs_remove(struct kernfs_node *kn)
kernfs_get(pos);
kernfs_drain(pos);
-
+ parent = kernfs_parent(pos);
/*
* kernfs_unlink_sibling() succeeds once per node. Use it
* to decide who's responsible for cleanups.
*/
- if (!pos->parent || kernfs_unlink_sibling(pos)) {
+ if (!parent || kernfs_unlink_sibling(pos)) {
struct kernfs_iattrs *ps_iattr =
- pos->parent ? pos->parent->iattr : NULL;
+ parent ? parent->iattr : NULL;
/* update timestamps on the parent */
down_write(&kernfs_root(kn)->kernfs_iattr_rwsem);
@@ -1722,7 +1738,7 @@ int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent,
int error;
/* can't move or rename root */
- if (!kn->parent)
+ if (!rcu_access_pointer(kn->__parent))
return -EINVAL;
root = kernfs_root(kn);
@@ -1733,8 +1749,15 @@ int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent,
(new_parent->flags & KERNFS_EMPTY_DIR))
goto out;
+ old_parent = kernfs_parent(kn);
+ if (root->flags & KERNFS_ROOT_INVARIANT_PARENT) {
+ error = -EINVAL;
+ if (WARN_ON_ONCE(old_parent != new_parent))
+ goto out;
+ }
+
error = 0;
- if ((kn->parent == new_parent) && (kn->ns == new_ns) &&
+ if ((old_parent == new_parent) && (kn->ns == new_ns) &&
(strcmp(kn->name, new_name) == 0))
goto out; /* nothing to rename */
@@ -1761,8 +1784,8 @@ int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent,
/* rename_lock protects ->parent and ->name accessors */
write_lock_irq(&kernfs_rename_lock);
- old_parent = kn->parent;
- kn->parent = new_parent;
+ old_parent = kernfs_parent(kn);
+ rcu_assign_pointer(kn->__parent, new_parent);
kn->ns = new_ns;
if (new_name) {
@@ -1795,7 +1818,8 @@ static struct kernfs_node *kernfs_dir_pos(const void *ns,
{
if (pos) {
int valid = kernfs_active(pos) &&
- pos->parent == parent && hash == pos->hash;
+ rcu_access_pointer(pos->__parent) == parent &&
+ hash == pos->hash;
kernfs_put(pos);
if (!valid)
pos = NULL;
diff --git a/fs/kernfs/kernfs-internal.h b/fs/kernfs/kernfs-internal.h
index b42ee6547cdc..c43bee18b79f 100644
--- a/fs/kernfs/kernfs-internal.h
+++ b/fs/kernfs/kernfs-internal.h
@@ -19,6 +19,8 @@
#include <linux/kernfs.h>
#include <linux/fs_context.h>
+extern rwlock_t kernfs_rename_lock;
+
struct kernfs_iattrs {
kuid_t ia_uid;
kgid_t ia_gid;
@@ -64,11 +66,14 @@ struct kernfs_root {
*
* Return: the kernfs_root @kn belongs to.
*/
-static inline struct kernfs_root *kernfs_root(struct kernfs_node *kn)
+static inline struct kernfs_root *kernfs_root(const struct kernfs_node *kn)
{
+ const struct kernfs_node *knp;
/* if parent exists, it's always a dir; otherwise, @sd is a dir */
- if (kn->parent)
- kn = kn->parent;
+ guard(rcu)();
+ knp = rcu_dereference(kn->__parent);
+ if (knp)
+ kn = knp;
return kn->dir.root;
}
@@ -97,6 +102,27 @@ struct kernfs_super_info {
};
#define kernfs_info(SB) ((struct kernfs_super_info *)(SB->s_fs_info))
+static inline bool kernfs_root_is_locked(const struct kernfs_node *kn)
+{
+ return lockdep_is_held(&kernfs_root(kn)->kernfs_rwsem);
+}
+
+static inline struct kernfs_node *kernfs_parent(const struct kernfs_node *kn)
+{
+ /*
+ * The kernfs_node::__parent remains valid within a RCU section. The kn
+ * can be reparented (and renamed) which changes the entry. This can be
+ * avoided by locking kernfs_root::kernfs_rwsem or kernfs_rename_lock.
+ * Both locks can be used to obtain a reference on __parent. Once the
+ * reference count reaches 0 then the node is about to be freed
+ * and can not be renamed (or become a different parent) anymore.
+ */
+ return rcu_dereference_check(kn->__parent,
+ kernfs_root_is_locked(kn) ||
+ lockdep_is_held(&kernfs_rename_lock) ||
+ !atomic_read(&kn->count));
+}
+
static inline struct kernfs_node *kernfs_dentry_node(struct dentry *dentry)
{
if (d_really_is_negative(dentry))
diff --git a/fs/kernfs/mount.c b/fs/kernfs/mount.c
index 4a0ff08d589c..2252b16e6ef0 100644
--- a/fs/kernfs/mount.c
+++ b/fs/kernfs/mount.c
@@ -148,7 +148,7 @@ static struct dentry *kernfs_get_parent_dentry(struct dentry *child)
struct kernfs_root *root = kernfs_root(kn);
guard(rwsem_read)(&root->kernfs_rwsem);
- return d_obtain_alias(kernfs_get_inode(child->d_sb, kn->parent));
+ return d_obtain_alias(kernfs_get_inode(child->d_sb, kernfs_parent(kn)));
}
static const struct export_operations kernfs_export_ops = {
@@ -188,10 +188,10 @@ static struct kernfs_node *find_next_ancestor(struct kernfs_node *child,
return NULL;
}
- while (child->parent != parent) {
- if (!child->parent)
+ while (kernfs_parent(child) != parent) {
+ child = kernfs_parent(child);
+ if (!child)
return NULL;
- child = child->parent;
}
return child;
@@ -216,7 +216,7 @@ struct dentry *kernfs_node_dentry(struct kernfs_node *kn,
dentry = dget(sb->s_root);
/* Check if this is the root kernfs_node */
- if (!kn->parent)
+ if (!rcu_access_pointer(kn->__parent))
return dentry;
root = kernfs_root(kn);
diff --git a/fs/kernfs/symlink.c b/fs/kernfs/symlink.c
index 45371a70caa7..05c62ca93c53 100644
--- a/fs/kernfs/symlink.c
+++ b/fs/kernfs/symlink.c
@@ -62,10 +62,10 @@ static int kernfs_get_target_path(struct kernfs_node *parent,
/* go up to the root, stop at the base */
base = parent;
- while (base->parent) {
- kn = target->parent;
- while (kn->parent && base != kn)
- kn = kn->parent;
+ while (kernfs_parent(base)) {
+ kn = kernfs_parent(target);
+ while (kernfs_parent(kn) && base != kn)
+ kn = kernfs_parent(kn);
if (base == kn)
break;
@@ -75,14 +75,14 @@ static int kernfs_get_target_path(struct kernfs_node *parent,
strcpy(s, "../");
s += 3;
- base = base->parent;
+ base = kernfs_parent(base);
}
/* determine end of target string for reverse fillup */
kn = target;
- while (kn->parent && kn != base) {
+ while (kernfs_parent(kn) && kn != base) {
len += strlen(kn->name) + 1;
- kn = kn->parent;
+ kn = kernfs_parent(kn);
}
/* check limits */
@@ -94,7 +94,7 @@ static int kernfs_get_target_path(struct kernfs_node *parent,
/* reverse fillup of target string from target to base */
kn = target;
- while (kn->parent && kn != base) {
+ while (kernfs_parent(kn) && kn != base) {
int slen = strlen(kn->name);
len -= slen;
@@ -102,7 +102,7 @@ static int kernfs_get_target_path(struct kernfs_node *parent,
if (len)
s[--len] = '/';
- kn = kn->parent;
+ kn = kernfs_parent(kn);
}
return 0;
@@ -111,12 +111,13 @@ static int kernfs_get_target_path(struct kernfs_node *parent,
static int kernfs_getlink(struct inode *inode, char *path)
{
struct kernfs_node *kn = inode->i_private;
- struct kernfs_node *parent = kn->parent;
+ struct kernfs_node *parent;
struct kernfs_node *target = kn->symlink.target_kn;
- struct kernfs_root *root = kernfs_root(parent);
+ struct kernfs_root *root = kernfs_root(kn);
int error;
down_read(&root->kernfs_rwsem);
+ parent = kernfs_parent(kn);
error = kernfs_get_target_path(parent, target, path);
up_read(&root->kernfs_rwsem);
diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
index 6931308876c4..c3d3b079aedd 100644
--- a/fs/sysfs/file.c
+++ b/fs/sysfs/file.c
@@ -19,13 +19,19 @@
#include "sysfs.h"
+static struct kobject *sysfs_file_kobj(struct kernfs_node *kn)
+{
+ guard(rcu)();
+ return rcu_dereference(kn->__parent)->priv;
+}
+
/*
* Determine ktype->sysfs_ops for the given kernfs_node. This function
* must be called while holding an active reference.
*/
static const struct sysfs_ops *sysfs_file_ops(struct kernfs_node *kn)
{
- struct kobject *kobj = kn->parent->priv;
+ struct kobject *kobj = sysfs_file_kobj(kn);
if (kn->flags & KERNFS_LOCKDEP)
lockdep_assert_held(kn);
@@ -40,7 +46,7 @@ static const struct sysfs_ops *sysfs_file_ops(struct kernfs_node *kn)
static int sysfs_kf_seq_show(struct seq_file *sf, void *v)
{
struct kernfs_open_file *of = sf->private;
- struct kobject *kobj = of->kn->parent->priv;
+ struct kobject *kobj = sysfs_file_kobj(of->kn);
const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
ssize_t count;
char *buf;
@@ -78,7 +84,7 @@ static ssize_t sysfs_kf_bin_read(struct kernfs_open_file *of, char *buf,
size_t count, loff_t pos)
{
struct bin_attribute *battr = of->kn->priv;
- struct kobject *kobj = of->kn->parent->priv;
+ struct kobject *kobj = sysfs_file_kobj(of->kn);
loff_t size = file_inode(of->file)->i_size;
if (!count)
@@ -105,7 +111,7 @@ static ssize_t sysfs_kf_read(struct kernfs_open_file *of, char *buf,
size_t count, loff_t pos)
{
const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
- struct kobject *kobj = of->kn->parent->priv;
+ struct kobject *kobj = sysfs_file_kobj(of->kn);
ssize_t len;
/*
@@ -131,7 +137,7 @@ static ssize_t sysfs_kf_write(struct kernfs_open_file *of, char *buf,
size_t count, loff_t pos)
{
const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
- struct kobject *kobj = of->kn->parent->priv;
+ struct kobject *kobj = sysfs_file_kobj(of->kn);
if (!count)
return 0;
@@ -144,7 +150,7 @@ static ssize_t sysfs_kf_bin_write(struct kernfs_open_file *of, char *buf,
size_t count, loff_t pos)
{
struct bin_attribute *battr = of->kn->priv;
- struct kobject *kobj = of->kn->parent->priv;
+ struct kobject *kobj = sysfs_file_kobj(of->kn);
loff_t size = file_inode(of->file)->i_size;
if (size) {
@@ -168,7 +174,7 @@ static int sysfs_kf_bin_mmap(struct kernfs_open_file *of,
struct vm_area_struct *vma)
{
struct bin_attribute *battr = of->kn->priv;
- struct kobject *kobj = of->kn->parent->priv;
+ struct kobject *kobj = sysfs_file_kobj(of->kn);
return battr->mmap(of->file, kobj, battr, vma);
}
@@ -177,7 +183,7 @@ static loff_t sysfs_kf_bin_llseek(struct kernfs_open_file *of, loff_t offset,
int whence)
{
struct bin_attribute *battr = of->kn->priv;
- struct kobject *kobj = of->kn->parent->priv;
+ struct kobject *kobj = sysfs_file_kobj(of->kn);
if (battr->llseek)
return battr->llseek(of->file, kobj, battr, offset, whence);
@@ -494,7 +500,7 @@ EXPORT_SYMBOL_GPL(sysfs_break_active_protection);
*/
void sysfs_unbreak_active_protection(struct kernfs_node *kn)
{
- struct kobject *kobj = kn->parent->priv;
+ struct kobject *kobj = sysfs_file_kobj(kn);
kernfs_unbreak_active_protection(kn);
kernfs_put(kn);
diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index 87c79d076d6d..5dda9a268e44 100644
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -147,6 +147,11 @@ enum kernfs_root_flag {
* Support user xattrs to be written to nodes rooted at this root.
*/
KERNFS_ROOT_SUPPORT_USER_XATTR = 0x0008,
+
+ /*
+ * Renames must not change the parent node.
+ */
+ KERNFS_ROOT_INVARIANT_PARENT = 0x0010,
};
/* type-specific structures for kernfs_node union members */
@@ -199,8 +204,8 @@ struct kernfs_node {
* never moved to a different parent, it is safe to access the
* parent directly.
*/
- struct kernfs_node *parent;
const char *name;
+ struct kernfs_node __rcu *__parent;
struct rb_node rb;
@@ -416,6 +421,7 @@ struct dentry *kernfs_node_dentry(struct kernfs_node *kn,
struct kernfs_root *kernfs_create_root(struct kernfs_syscall_ops *scops,
unsigned int flags, void *priv);
void kernfs_destroy_root(struct kernfs_root *root);
+unsigned int kernfs_root_flags(struct kernfs_node *kn);
struct kernfs_node *kernfs_create_dir_ns(struct kernfs_node *parent,
const char *name, umode_t mode,
@@ -514,6 +520,8 @@ kernfs_create_root(struct kernfs_syscall_ops *scops, unsigned int flags,
{ return ERR_PTR(-ENOSYS); }
static inline void kernfs_destroy_root(struct kernfs_root *root) { }
+static inline unsigned int kernfs_root_flags(struct kernfs_node *kn)
+{ return 0; }
static inline struct kernfs_node *
kernfs_create_dir_ns(struct kernfs_node *parent, const char *name,
diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c
index e28d5f0d20ed..c9752eb607ec 100644
--- a/kernel/cgroup/cgroup-v1.c
+++ b/kernel/cgroup/cgroup-v1.c
@@ -844,7 +844,7 @@ static int cgroup1_rename(struct kernfs_node *kn, struct kernfs_node *new_parent
if (kernfs_type(kn) != KERNFS_DIR)
return -ENOTDIR;
- if (kn->parent != new_parent)
+ if (rcu_access_pointer(kn->__parent) != new_parent)
return -EIO;
/*
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index d9061bd55436..71819e58d70c 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -633,9 +633,22 @@ int cgroup_task_count(const struct cgroup *cgrp)
return count;
}
+static struct cgroup *kn_priv(struct kernfs_node *kn)
+{
+ struct kernfs_node *parent;
+ /*
+ * The parent can not be replaced due to KERNFS_ROOT_INVARIANT_PARENT.
+ * Therefore it is always safe to dereference this pointer outside of a
+ * RCU section.
+ */
+ parent = rcu_dereference_check(kn->__parent,
+ kernfs_root_flags(kn) & KERNFS_ROOT_INVARIANT_PARENT);
+ return parent->priv;
+}
+
struct cgroup_subsys_state *of_css(struct kernfs_open_file *of)
{
- struct cgroup *cgrp = of->kn->parent->priv;
+ struct cgroup *cgrp = kn_priv(of->kn);
struct cftype *cft = of_cft(of);
/*
@@ -1612,7 +1625,7 @@ void cgroup_kn_unlock(struct kernfs_node *kn)
if (kernfs_type(kn) == KERNFS_DIR)
cgrp = kn->priv;
else
- cgrp = kn->parent->priv;
+ cgrp = kn_priv(kn);
cgroup_unlock();
@@ -1644,7 +1657,7 @@ struct cgroup *cgroup_kn_lock_live(struct kernfs_node *kn, bool drain_offline)
if (kernfs_type(kn) == KERNFS_DIR)
cgrp = kn->priv;
else
- cgrp = kn->parent->priv;
+ cgrp = kn_priv(kn);
/*
* We're gonna grab cgroup_mutex which nests outside kernfs
@@ -2118,7 +2131,8 @@ int cgroup_setup_root(struct cgroup_root *root, u16 ss_mask)
root->kf_root = kernfs_create_root(kf_sops,
KERNFS_ROOT_CREATE_DEACTIVATED |
KERNFS_ROOT_SUPPORT_EXPORTOP |
- KERNFS_ROOT_SUPPORT_USER_XATTR,
+ KERNFS_ROOT_SUPPORT_USER_XATTR |
+ KERNFS_ROOT_INVARIANT_PARENT,
root_cgrp);
if (IS_ERR(root->kf_root)) {
ret = PTR_ERR(root->kf_root);
@@ -4119,7 +4133,7 @@ static ssize_t cgroup_file_write(struct kernfs_open_file *of, char *buf,
size_t nbytes, loff_t off)
{
struct cgroup_file_ctx *ctx = of->priv;
- struct cgroup *cgrp = of->kn->parent->priv;
+ struct cgroup *cgrp = kn_priv(of->kn);
struct cftype *cft = of_cft(of);
struct cgroup_subsys_state *css;
int ret;
diff --git a/tools/testing/selftests/bpf/progs/profiler.inc.h b/tools/testing/selftests/bpf/progs/profiler.inc.h
index 8bd1ebd7d6af..813143b4985d 100644
--- a/tools/testing/selftests/bpf/progs/profiler.inc.h
+++ b/tools/testing/selftests/bpf/progs/profiler.inc.h
@@ -223,7 +223,7 @@ static INLINE void* read_full_cgroup_path(struct kernfs_node* cgroup_node,
if (bpf_cmp_likely(filepart_length, <=, MAX_PATH)) {
payload += filepart_length;
}
- cgroup_node = BPF_CORE_READ(cgroup_node, parent);
+ cgroup_node = BPF_CORE_READ(cgroup_node, __parent);
}
return payload;
}
generated by cgit v1.2.3 (git 2.46.0) at 2025-07-31 14:00:32 +0000